There are several limitations which should be considered when interpreting the results of this study, or if this study was to be replicated in future. Firstly, only 25 participants out of the 44 CI users from the SCIP who fulfilled the participant inclusion criteria were able to participate in the study. Many of the participants lived out of the city, and scheduling a time for them to attend a testing session at the University Clinic was often unfeasible. Some of the participants could not be contacted to arrange for a testing session, whilst others were not coming into the city during the time period of this study. A longer time frame or a follow-up study could have helped recruit a greater number of participants.
Secondly, pre-surgery testing was performed using 5 dB steps where as post-surgery testing was done using 2 dB steps. Using 2 dB steps in at least one pre-surgery test is recommended for future clinical assessment in order to provide greater accuracy when comparing to post-surgery thresholds. This will be particularly relevant when the surgeons want to assess the effectiveness of any modified surgical techniques or procedures. To allow for control over factors such as the progressive loss of hearing levels post-surgery, a longitudinal research design could be adopted where pre- and
post-surgery hearing tests are conducted at specific time intervals post-implantation for al the participants (e.g. 1 month, 3 months, 6 months, 12 months etc.).
Thirdly, none of the 13 participants that presented with residual hearing were currently using a HA in conjunction with the CI. A future study to evaluate the potential benefit that the HA may provide could be done using these participants with the results compared to this study.
The clinical implications of the results from the current research include that current, as well as future implantees through the SCIP who present with residual hearing should be encouraged to use a HA in their contralateral ear, along with their CI. This would allow them to maximise the benefits of both electric as well as low-frequency acoustic hearing. Additionally, the results from this study could be used to evaluate the efficacy of the new modified surgical techniques or strategies that the surgeons in the SCIP are beginning to implement. Should there be a further improvement in post-surgery outcomes, this could translate into expanding the candidacy criteria for a CI to include those persons with better hearing thresholds.
Finally, this study has demonstrated that like many overseas programs, cochlear implantation in New Zealand provides significant speech perception benefit for those with a significant sensorineural hearing loss. The mean open-set sentence perception improvement from 19% pre-surgery to 82% post-surgery is a clinically significant change. This along with the suggestion of potentially even better post-surgery outcomes in the future could be used to lobby the government for increased funding to the CI
program. This would not only be to address the current waiting list, but to enable more people who could potentially benefit from a CI to be afforded the opportunity to obtain one.
Summary and conclusion
This study found that even in the absence of specific hearing preservation techniques being used during implantation surgery for participants of this study, some of the participants still presented with measurable levels of post-surgery residual hearing. Thirteen of the 25 participants (52%) presented with measurable levels of acoustic hearing in their implanted ear. Further, 13 participants had aidable hearing in their contralateral ear. The speech perception results obtained from this study suggest that these implant recipients are obtaining significant improvement in speech perception outcomes post-surgery. The current SCIP candidacy criteria for cochlear implantation includes having pre-surgery speech perception scores less than 40% correct in the best- aided condition, and less than 60% correct in the ear to be implanted. The significant pre- to post-surgery improvement in speech perception outcomes for the participants of our study is a clear reflection that the current speech criteria for used by the SCIP to evaluate cochlear implant candidacy is not too lenient.
This thesis has also suggested that current, as well as future implantees through the SCIP who present with residual hearing in their contralateral ear should be encouraged to use a HA along with their CI. This would allow them to maximise the benefits of both electric as well as low-frequency acoustic hearing. Furthermore, should there be a future improvement in post-surgery outcomes resulting from the new modified surgical techniques or strategies that the surgeons in the SCIP are beginning to implement, this could translate into expanding theSCIP’scandidacy criteria for a CI. However, this
would probably require additional funding in order to ensure that there are sufficient resources for increased patient numbers. The speech perception benefits demonstrated in this and many similar studies, along with the quality of life reported by a host of studies (Cohen, Labadie, Dietrich, & Haynes, 2004; Damen, Beynon, Krabbe, Mulder, & Mylanus, 2007; Mo, Lindbaek, Harris, & Rasmussen, 2004) should be communicated to the government and other funding bodies. With the continual improvements in CI outcomes, more hearing impaired people are, and will continue to benefit from a CI.
Balkany, T. J., Connell, S. S., Hodges, A. V., Payne, S. L., Telischi, F. F., Eshraghi, A. A., et al. (2006). Conservation of residual acoustic hearing after cochlear implantation. Otology & Neurotology, 27(8), 1083-1088.
Balkany, T. J., Eshraghi, A. A., Jiao, H., Polak, M., Mou, C., Dietrich, D. W., et al. (2005). Mild hypothermia protects auditory function during cochlear implant surgery. Laryngoscope, 115(9), 1543-1547.
Berrettini, S., Forli, F., & Passetti, S. (2007). Preservation of residual hearing following cochlear implantation: comparison between three surgical techniques. J
Laryngology & Otology, 1-7.
Britannica, E. bony labyrinth. Retrieved 14/12/2007, from http://www.britannica.com/eb/art-532
Britannica, E. cochlea: cross section. Retrieved 14/12/2007, from http://www.britannica.com/eb/art-534
Carhart, R., & Jerger, J. F. (1959). Preffered method for the clinical determination of pure-tone thresholds. Journal of Speech and Hearing Disorders, 24, 330-345. Ching, T. Y., Incerti, P., & Hill, M. (2004). Binaural benefits for adults who use hearing
aids and cochlear implants in opposite ears. Ear and Hearing, 25(1), 9-21. Chivukula, K., Laulicht, B., Marcello, D., Patel, R., & Saphirstein, R. (2006). Speech
processor. Retrieved 14/12/2007, from
Clarke, B. G., Franz, B. K.-H. G., Pyman, B. C., & Webb, R. L. (1991). Surgery for multichannel cochlear implantation. In H. Cooper (Ed.), Cochlear Implants: A Practical Guide (1st ed., pp. 169-200). London: Whurr Publishers Ltd.
Cochlear (2005). Product Photos. Retrieved 14/12/2007, from http://www.cochlearamericas.com/corporate/press/186.asp
Cohen, S. M., Labadie, R. F., Dietrich, M. S., & Haynes, D. S. (2004). Quality of life in hearing-impaired adults: the role of cochlear implants and hearing aids.
Damen, G. W., Beynon, A. J., Krabbe, P. F., Mulder, J. J., & Mylanus, E. A. (2007). Cochlear implantation and quality of life in postlingually deaf adults: long-term follow-up. Otolaryngology Head and Neck Surgery, 136(4), 597-604.
Di Nardo, W., Cantore, I., Melillo, P., Cianfrone, F., Scorpecci, A., & Paludetti, G. (2007). Residual hearing in cochlear implant patients. European Archives of Otorhinolaryngology, 264(8), 855-860.
Dorman, M. F., Spahr, A. J., Loizou, P. C., Dana, C. J., & Schmidt, J. S. (2005). Acoustic simulations of combined electric and acoustic hearing (EAS). Ear and Hear, 26(4), 371-380.
Dowell, R. C., Hollow, R., & Winton, E. (2004). Outcomes for cochlear implant users with significant residual hearing: implications for selection criteria in children. Archives of Otolaryngology-Head & Neck Surgery, 130(5), 575-581.
Dowell, R. C., Martin, L. F., Clark, G. M., & Brown, A. M. (1985). Results of a preliminary clinical trial on a multiple channel cochlear prosthesis. Annals of Otology, Rhinology & Laryngology, 94(3), 244-250.
Flynn, M. C., Dowell, R. C., & Clark, G. M. (1998). Aided speech recognition abilities of adults with a severe or severe-to-profound hearing loss. Journal of Speech Language and Hearing Research, 41(2), 285-299.
Foundation, L. T. H. (2004). Cochlear implant surgery. Retrieved 24/12/2007, from http://www.letthemhear.org/images/flash_demos/surgical/menu.html
Frank, T. (2000). ANSI update: maximum permissible ambient noise levels for audiometric test rooms. American Journal of Audiology, 9(1), 3-8.
Fraysse, B., Dillier, N., Klenzner, T., Laszig, R., Manrique, M., Morera Perez, C., et al. (1998). Cochlear implants for adults obtaining marginal benefit from acoustic amplification: a European study. American Journal of Otology, 19(5), 591-597. Fraysse, B., Macias, A. R., Sterkers, O., Burdo, S., Ramsden, R., Deguine, O., et al.
(2006). Residual hearing conservation and electroacoustic stimulation with the nucleus 24 contour advance cochlear implant. Otology & Neurotology, 27(5), 624-633.
Friesen, L. M., Shannon, R. V., Baskent, D., & Wang, X. (2001). Speech recognition in noise as a function of the number of spectral channels: comparison of acoustic hearing and cochlear implants. Journal of Acoustical Society of America, 110(2), 1150-1163.
Fu, Q. J., Shannon, R. V., & Wang, X. (1998). Effects of noise and spectral resolution on vowel and consonant recognition: acoustic and electric hearing. Journal of Acoustical Society of America, 104(6), 3586-3596.
Gantz, B. J., Turner, C., Gfeller, K. E., & Lowder, M. W. (2005). Preservation of hearing in cochlear implant surgery: advantages of combined electrical and acoustical speech processing. Laryngoscope, 115(5), 796-802.
Gantz, B. J., & Turner, C. W. (2003). Combining acoustic and electrical hearing. Laryngoscope, 113(10), 1726-1730.
Gantz, B. J., Tyler, R. S., Knutson, J. F., Woodworth, G., Abbas, P., McCabe, B. F., et al. (1988). Evaluation of five different cochlear implant designs: audiologic assessment and predictors of performance. Laryngoscope, 98(10), 1100-1106. Gantz, B. J., Woodworth, G. G., Knutson, J. F., Abbas, P. J., & Tyler, R. S. (1993).
Multivariate predictors of audiological success with multichannel cochlear implants. Annals of Otology, Rhinology & Laryngology, 102(12), 909-916. Gifford, R. H., Shallop, J. K., Driscoll, C. L. W., Peterson, A. M., Beatty, C. W., &
Lane, J. L. (2007). Comparative results in the hearing preservation for patients with the Nucleus CI24 Vs. Nucleus CI24RE Hybrid. In 2007 Conference on Implantable Auditory Prosthesis. Lake Tahoe, California, USA.
Gomaa, N. A., Rubinstein, J. T., Lowder, M. W., Tyler, R. S., & Gantz, B. J. (2003). Residual speech perception and cochlear implant performance in postlingually deafened adults. Ear and Hearing, 24(6), 539-544.
Green, K. M., Bhatt, Y. M., Mawman, D. J., O'Driscoll, M. P., Saeed, S. R., Ramsden, R. T., et al. (2007). Predictors of audiological outcome following cochlear implantation in adults. Cochlear Implants International, 8(1), 1-11. Hamzavi, J., Baumgartner, W. D., Pok, S. M., Franz, P., & Gstoettner, W. (2003).
Variables affecting speech perception in postlingually deaf adults following cochlear implantation. Acta Otolaryngology, 123(4), 493-498.
Healthwise. Hearing aid. Retrieved 11/02/2008, fromhttp://health.yahoo.com/hearing- resources/hearing-aid/healthwise--zm6101.html
Hochmair, I., Nopp, P., Jolly, C., Schmidt, M., Schosser, H., Garnham, C., et al. (2006). MED-EL Cochlear implants: state of the art and a glimpse into the future. Trends in Amplification, 10(4), 201-219.
Hodges, A. V., Schloffman, J., & Balkany, T. (1997). Conservation of residual hearing with cochlear implantation. American Journal of Otology, 18(2), 179-183. James, C., Albegger, K., Battmer, R., Burdo, S., Deggouj, N., Deguine, O., et al. (2005).
Preservation of residual hearing with cochlear implantation: how and why. Acta Otolaryngology, 125(5), 481-491.
James, C. J., Fraysse, B., Deguine, O., Lenarz, T., Mawman, D., Ramos, A., et al. (2006). Combined electroacoustic stimulation in conventional candidates for cochlear implantation. Audiology & Neurootology, 11 Suppl 1, 57-62.
Kiefer, Gstoettner, W., Baumgartner, W., Pok, S. M., Tillein, J., Ye, Q., et al. (2004). Conservation of low-frequency hearing in cochlear implantation. Acta
Otolaryngology, 124(3), 272-280.
Loizou, P. C. (1999). Signal-processing techniques for cochlear implants. IEEE Eng Med Biol Mag, 18(3), 34-46.
Loizou, P. C. (2006). Speech processing in vocoder-centric cochlear implants Advances in Otorhinolaryangology, 64, 109-143.
Luetje, C. M., Thedinger, B. S., Buckler, L. R., Dawson, K. L., & Lisbona, K. L. (2007). Hybrid cochlear implantation: clinical results and critical review in 13 cases. Otology & Neurotology, 28(4), 473-478.
Luntz, M., Shpak, T., & Weiss, H. (2005). Binaural-bimodal hearing: concomitant use of a unilateral cochlear implant and a contralateral hearing aid. Acta
Otolaryngology, 125(8), 863-869.
McDermott, H. J., McKay, C. M., & Vandali, A. E. (1992). A new portable sound processor for the University of Melbourne/Nucleus Limited multielectrode cochlear implant Journal of Acoustical Society of America, 91(6), 3367-3371. Mo, B., Lindbaek, M., Harris, S., & Rasmussen, K. (2004). Social hearing measured
with the Performance Inventory for Profound and Severe Loss: a comparison between adult multichannel cochlear implant patients and users of acoustical hearing aids. International Journal of Audiology, 43(10), 572-578.
Mok, M., Grayden, D., Dowell, R. C., & Lawrence, D. (2006). Speech perception for adults who use hearing aids in conjunction with cochlear implants in opposite ears. Journal of Speech Language and Hearing Research, 49(2), 338-351. Munson, B., & Nelson, P. B. (2005). Phonetic identification in quiet and in noise by
listeners with cochlear implants. Journal of Acoustical Society of America, 118(4), 2607-2617.
National Institute of Health Consensus Development Conference. (1995). Cochlear implants in adults and children. Journal of the American Medical Association, 274(24), 1955-1961.
Nilsson, M., Soli, S. D., & Sullivan, J. A. (1994). Development of the Hearing in Noise Test for the measurement of speech reception thresholds in quiet and in noise. Journal of Acoustical Society of America, 95(2), 1085-1099.
Pau, H. W., Just, T., Bornitz, M., Lasurashvilli, N., & Zahnert, T. (2007). Noise exposure of the inner ear during drilling a cochleostomy for cochlear implantation. Laryngoscope, 117(3), 535-540.
Peterson, G. E., & Lehiste, I. (1962). Revised CNC Lists for Auditory tests. Journal of Speech Hearing Disorders, 27, 62-70.
Rappaport, J. M., & Provencal, C. (2002). Neuro-otology for Audiologists. In J. Katz (Ed.), Handbook of Clinical Audiology (5th ed., pp. 9-32). Baltimore: Lippincott Williams & Wilkins.
Rizer, F. M., Arkis, P. N., Lippy, W. H., & Schuring, A. G. (1988). A postoperative audiometric evaluation of cochlear implant patients. Otolaryngolgy Head &Neck Surgery, 98(3), 203-206.
Roland, P. S., Gstottner, W., & Adunka, O. (2005). Method for hearing preservation in cochlear implant surgery. Operative Techniques in Otolaryngology (16), 93-100. Ronald, P. S., & Wright, C. S. (2006). Surgical aspects of Cochlear Implantation:
Mechanisms of Insertional Trauma. Advances in Otorhinolaryngology. Ruffin, C. V., Tyler, R. S., Witt, S. A., Dunn, C. C., Gantz, B. J., & Rubinstein, J. T.
(2007). Long-term performance of Clarion 1.0 cochlear implant users. Laryngoscope, 117(7), 1183-1190.
Skarzynski, H., Lorens, A., Piotrowska, A., & Anderson, I. (2007). Preservation of low frequency hearing in partial deafness cochlear implantation (PDCI) using the round window surgical approach. Acta Otolaryngology, 127(1), 41-48.
Skinner, M. W., Clark, G. M., Whitford, L. A., Seligman, P. M., Staller, S. J., Shipp, D. B., et al. (1994). Evaluation of a new spectral peak coding strategy for the Nucleus 22 Channel Cochlear Implant System. American Journal of Otology, 15 Suppl 2, 15-27.
Smith, Z. M., Delgutte, B., & Oxenham, A. J. (2002). Chimaeric sounds reveal dichotomies in auditory perception. Nature, 416(6876), 87-90.
Stickney, G. S., Zeng, F. G., Litovsky, R., & Assmann, P. (2004). Cochlear implant speech recognition with speech maskers. Journal of Acoustical Society of America, 116(2), 1081-1091.
Summerfield, A. Q., & Marshall, D. H. (1995). Preoperative predictors of outcomes from cochlear implantation in adults: performance and quality of life. Annals of Otology, Rhinology and Laryngology Supplement, 166, 105-108.
Tyler, R. S., Parkinson, A. J., Wilson, B. S., Witt, S., Preece, J. P., & Noble, W. (2002). Patients utilizing a hearing aid and a cochlear implant: speech perception and localization. Ear and Hearing, 23(2), 98-105.
Understanding the Audiogram. from
http://www.lhh.org/about_hearing_loss/understanding/audiogram.html van Dijk, J. E., van Olphen, A. F., Langereis, M. C., Mens, L. H., Brokx, J. P., &
Smoorenburg, G. F. (1999). Predictors of cochlear implant performance. Audiology, 38(2), 109-116.
Vandali, A. E., Whitford, L. A., Plant, K. L., & Clark, G. M. (2000). Speech Perception as a Function of Electrical Stimulation Rate: Using the Nucleus 24 Cochlear Implant System. Ear and Hearing, 21, 608-624.
von Ilberg, C., Kiefer, J., Tillein, J., Pfenningdorff, T., Hartmann, R., Sturzebecher, E., et al. (1999). Electric-acoustic stimulation of the auditory system. New
technology for severe hearing loss. Journal for oto-rhino-laryngology and its related specialties, 61(6), 334-340.
Waltzman, S. B., Cohen, N. L., & Shapiro, W. H. (1993). The benefits of cochlear implantation in the geriatric population. Otolaryngology Head & Neck Surgery, 108(4), 329-333.
Waltzman, S. B., Fisher, S. G., Niparko, J. K., & Cohen, N. L. (1995). Predictors of postoperative performance with cochlear implants. Annals of Otology, Rhinology and Laryngology Supplement, 165, 15-18.
What is a cochlear implant. Retrieved 11/02/2008, from
Yao, W. N., Turner, C. W., & Gantz, B. J. (2006). Stability of low-frequency residual hearing in patients who are candidates for combined acoustic plus electric hearing. Journal of Speech Language and Hearing Research, 49(5), 1085-1090. Yost, W. A. (2000). Fundamentals of Hearing an Introduction (4th ed.). San Diego:
(A) Pre-surgery thresholdsImplanted ear P articipant 250 H z 500 H z 750H z 1000 H z 1500H z 2000 H z 3000 H z 4000 H z 6000 H z 8000 H z 1 60 80 90 95 90 85 80 95 N R N R 2 60 70 80 105 120 N R 115 N R N R 3 65 75 85 100 105 110 120 N R N R N R 4 55 75 95 100 115 N R N R N R N R N R 5 60 70 85 105 110 105 120 115 N R N R 6 30 35 95 100 105 105 N R N R N R 95 7 55 55 65 65 70 95 110 N R 8 20 90 105V T 120 115V T N R 9 65 70 90 110 N R N R N R N R 10 65 75 90 95 95 90 95 100 N R N R 11 90 100 95 110 95 100 90 12 70 80 85 90 110 N R N R N R N R N R 13 65 70 85 90 95 N R N R N R N R N R 14 50 105 115 115 115 115 110 105 15 100 100 110 110 115 N R N R N R N R 16 100 105 115 110 115 N R N R N R N R N R 17 N R 95 N R N R N R N R N R N R N R N R 18 35 65 85 105 120 120 115 N R N R N R 19 70 85 95 100 N R N R N R N R N R N R 20 95 95 95 95 90 90 90 90 95 95 21 75 95 105 105 110 115 115 N R N R N R 22 80 80 90 75 75 65 23 45 95 110 115 120 120 120 N R N R N R 24 75 100 115 115 N R N R N R N R N R 25 15 80 105 110 115 115 115 N R N R
Unimplanted ear Participant 250 Hz 500 Hz 750Hz 1000 Hz 1500Hz 2000 Hz 3000 Hz 4000 Hz 6000 Hz 8000 Hz 1 60 100 NR 100 110 115 120 NR NR NR 2 85 90 95 120 NR NR NR NR NR 3 65 80 100 105 110 110 115 NR NR NR 4 85 85 90 95 100 105 110 110 NR NR 5 50 60 80 110 110 115 105 NR NR 6 40 55 70 95 110 110 115 NR NR NR 7 60 60 75 80 75 80 85 100 105 8 15 45 90 110 120 NR NR NR 9 50 55 90 110 90 100 NR NR 10 NR NR NR NR NR NR NR NR NR NR 11 NR NR NR NR NR NR NR NR NR NR 12 65 75 75 80 90 105 NR 110 NR NR 13 65 70 95 90 90 NR NR NR NR NR 14 20 70 110 110 110 115 NR NR 15 85 90 95 105 115 NR NR NR NR 16 NR 105 110 110 110 NR NR NR NR NR 17 NR NR NR NR NR NR NR NR NR NR 18 45 55 65 80 115 110 110 NR NR NR 19 110 NR 115 110 120 110 105 120 NR NR 20 110 105 105 110 NR NR NR NR NR NR 21 100 110 110 110 110 115 NR NR NR NR 22 20 35 75 95 90 90 70 60 23 45 100 110 115 110 120 120 NR NR NR 24 65 90 110 105 100 100 95 95 80 25 10 45 105 105 115 115 110 NR NR